convert them to improper fractions (bigger number on top) first
12 * 4 + 1 = 25 so 12 1/4 = 25/4
4 * 8 + 6 = 38 so 4 6/8 = 38/8
now you have 25/4 - 38/8
the bottoms (denominators) are different
4 goes into 8, so multiply the top (numerator) and bottom of 25/4 by 2
50/8 - 38/8
the bottoms are the same now, so we can combine the tops like this
(50-38) / 8
12 / 8
reduce. divide the top and bottom by 4
3/2
1 1/2